This Earthcache has been set to highlight a unique natural feature. At the coordinates you’ll find a white post that used to have a small information panel relating to this cache. It stated that if the temperature reached 0° C the statue on the flood wall would be dressed in a red coat.
The Barber
"The Barber" is a katabatic wind, cold as ice and cutting to the bone. It's said to be able to shave the hair off a man's face, hence the name it goes by.
Cold wind streams down the Grey Valley in the morning from up to 50km inland when there is a southeast flow over the South Island of New Zealand.
It then funnels through the tight Grey River/Mawheranui gap between two impressive uplifts, the Cobden Range to the north and the Omoto Range to the south just behind the town, then aiming it straight at the central business district of Greymouth as it finds its way out to sea.
It is marked by a trail of white mist that creeps over the surrounding hills, making for some dramatic photographs. It’s one of only a few locations around the world where this occurs, it is a beautiful but chilly natural wonder.
A katabatic wind (named from the Greek word katabasis, it means "descending".) is the technical name for a drainage wind, a wind that carries high-density air from a higher elevation down a slope under the force of gravity. Such winds are sometimes also called fall winds. The spelling “catabatic winds” is also used. Katabatic winds can rush down elevated slopes at hurricane speeds, but most are not as intense as that, and many are 10 knots (18 km/h) or less.
A katabatic wind like "the Barber" originates from the cooling of air through radiation atop a plateau, a mountain, glacier, or even a hill. Since the density of air is inversely proportional to temperature, the air will flow downwards adiabatically (occurring without gain or loss of heat) as it descends. The temperature of the air depends on the temperature in the source region and the amount of descent.
Convolutions of terrain tend to make for significant complexities in airflow. Anyone who has ventured upland moors, alpine plateaus and glacier-sharpened ridge spines is well-acquainted with highland winds, which can be ferocious, frigid and desolating. While many such breezes and gusts stem mainly from variations in atmospheric pressure, some are simply the gravitational tumble of air parcels -- called katabatic winds.
Katabatic winds are also occasionally referred to as gravity-driven winds, a moniker that concisely explains their nature. They form as air over cold uplands spills downward into adjacent lowlands; air becomes denser with decreasing temperature, and thus succumbs to gravitational force. Katabatic winds are similar to a host of other localized air movements in rugged country, such as the daily and nightly reversals of mountain and valley breezes, but the latter arise because of atmospheric pressure differences due to differential solar heating. For instance, winds such as the Föhn, and Chinook are rain shadow winds where air driven upslope on the windward side of a mountain range drops its moisture and descends leeward drier and warmer.
Examples of true katabatic winds include the Bora (or Bura) in the Adriatic, the Bohemian Wind or Böhmwind in the Ore Mountains, the Santa Ana in southern California, the Piteraq winds of Greenland, the Oroshi in Japan and "the Barber", that blows in New Zealand.
Logging requirements:
You may log your find as soon as you've sent your answers, no need to wait. You'll be contacted if there are any problems.
Forward the answers to the following questions to the CO using E-mail or the Message Centre. Please don't include the answers in your online log.
- Katabatic winds are similar to other localized air movements in rugged country. Explain the different reasons of why they form.
- Explain the meaning of adiabatical airflow. When, why and how does it occur.
- Why do you think that "the Barber" only creates a trail of mist over the Grey River after it flowed through the Mawheranui Gap and tumbled over the uplifts?.
- Please include with your log a photo of you, your GPS or both with the Grey River/Mawheranui gap in the background.
References:
Creative Commons Attribution-Noncommercial-Share Alike 3.0 New Zealand License
https://en.wikipedia.org/wiki/Katabatic_wind
https://sciencing.com/causes-katabatic-winds-22602.html